Petrological (Polarizing, Mineral) Microscope, c. 1898
While this particular model with all its features
is not illustrated in either the 1885 or 1903
Seibert catalogs, it conforms to the middle
polarizing model IIb described in the 1903 catalog with the analyzing prism mounted in the tube,
but with the addition of a Bertrand lens. It features a
substage polarizing condenser with a removable top
element that is focused using a lever mechanism, an
analyzing prism mounted in the tube in a slide-in
holder, a centerable rotating stage with calibrations
in degrees with vernier, and a focusing slot which holds
a Bertrand lens. An additional slot is provided that
accommodates the compensator plates; two are provided. In addition, it comes with two Seibert objectives, two eyepieces, and for conventional microscopy, an aperture stop holder with three stops. Another, less
complicated,
polarizing microscope of similar vintage is also
represented in the collection.